This season's Champions League final at Wembley will be played between the Bundesliga champions and their counterparts Borussia Dortmund.

The post-mortem for the Spaniards will be vigorous: is it the end of an era? Is a changing of the guard required?

We look back at our La Liga expert David Cartlidge's view of where it all went wrong for the former greatest team in the world....

Barça are so used to people looking at them with awe, but now the club needs to take a look at itself.

They need to evolve once more, retain their values but somehow add something new to get them back on top again.

The defeats against Bayern were really a second chapter after the defeat to Chelsea last season at the same stage of the Champions League. The problems that arose in that game still haven’t been addressed. As stunning and shocking as the defeats to Bayern were, the warning signs were there 12 months ago when Roberto Di Matteo's side bested them on their way to the trophy.

The warning signs were there: Torres helps knock Barcelona out last year (Photo: Reuters)

Of course, Lionel Messi’s fitness problems particularly left Barça wide open as the little Argentinean's brilliance has blinded everyone from the real troubles the team has.

The likes of Xavi, David Villa and Pedro have been stuttering for two years, while others like Gerard Piqué haven’t been beacons of consistency. Messi has been compensating for these players, covering over each little crack at Camp Nou with each little dazzling run across the turf. But when he was finally broken himself, Barça's problems were exposed.

The fundamentals of the system that captured everyone's imagination: pressing, incisiveness, ruthlessness, fitness, were all absent against Bayern. The Germans showed again they are the prototype team now, harnessing all those aspects but adding their own devastating touches including physical dominance, organisation and intelligence.

Barça were still playing their game but they found it’s not enough anymore; it has become predictable and diluted – frighteningly, the trend setters, the bar raisers, have found themselves left behind.

Like Messi, Busquets has become a vital cog in the works of this team. If there has been minimal evolution at Barca, it is found in his role. But he was also absent tonight. And, in prior games against Milan and PSG, he has been left exposed by Xavi and to a lesser extent, Iniesta.

They don’t press or show that aggression with the defensive side of their game resulting in Barça being weighed down by another two passengers. Busquets’ emergence has been exhilarating, but is absence was also cruelly felt.

Sergio Busquets: Doing his best but he can't do it all (Photo: Christof Koepsel)

Xavi perhaps epitomises Barça’s situation, his legs are not the power houses they once were and only belatedly are the club dealing with the situation. Cesc Fábregas and Thiago should have had bigger roles by now, and almost certainly will next season. Xavi, as remarkable as he’s been for years, needs to pass – no pun intended – the baton.

Tito Vilanova will be the man to oversee any changes as his position won’t come under scrutiny at the moment. But it will if he doesn’t address the regression/stagnation of this team.

Under him Barça have come from behind on 13 occasions this season – a 14th at Camp Nou against Bayern proved impossible.

Tito needs support from the men in power though, as Barça need a successful summer to improve their squad. No settling for second, third, or fourth best. They need to sign their top targets.

Javi Martínez, a player whom Barça’s players identified themselves as man who would fit the team’s functions, again powered through the Bayern midfield with power and purpose, they could only watch on and wonder what could have been.

Instead, austerity was cited and the cheap route taken. Martínez was €40m, but what price do you put on the team being left behind? Some at Barça need to ask themselves that very question.

This summer is a crucial one if they are to regain their place at the summit of European football next season. And perhaps now, the men in charge know that.

As dark as these times are, Barça have hopefully seen the light in terms of their future.